Key sender test circuit



June 25, 1957 H. REAGAN KEY SENDER TEST CIRCUIT 12 Sheets-Sheet l Filed 001'.. 28, 1952 l June 25, 1957 I.. H. REAGAN 2,797,268

' KEY SENDER TEST CIRCUIT Filed Oct. 28, 1952 i2 Sheets-Sheet 2 I C-ONTROL KEYS ZO-l.I v 2IO 220 2 O 2 O ISRI' 4 I I I I I I I I I I I I CONTROL RELAYS E A I-I I I I l I I M I IIJ Irl

PURy

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- L .REA A TEST EQUIPMENT l EON H G N F l G Z ATTORNEY June 25, 1957 L. H. REAGAN 2,797,268

KEY SENDER TEST CIRCUIT Filed Oct. 28, 1952 12 Sheets-Sheet 3 FIG. 3

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L. H. REAGAN KEY SENDER TEST CIRCUIT 12 Sheets-Sheet 4 JACK TERMINALS I 0N TEST EQUIPMENT DELAY I I I I RELEASE LFG couN'T/NG LAMPS TEST EQUIPMENT STEPPINc,` MAGNET L4 A I I j RELEASE MAGNET Bym PURl

442 44, MINOR swITcH oFF-NORMAL Q coNTAcTS I 463/* si PU MT A INVENTOR. H. REAGAN MMI ATTORNEY June 25, 1957 I.. H. REAGAN KEY SENDER TEST CIRCUIT 'Filed Oct. 28. 1952 12 Sheets-Sheet 5 PATcHING coRo 400 sENDER FIG.5

. LEON H. REAGAN ATTORNEY ATTORNEY 12 Sheets-Sheet 6 INVENTOR. LEON H. REAGAN June 25, 1957 L. H.V REAGAN KEY SENDER TEST CIRCUIT Filed oct. 2a, 1952 L T T G T mm u H Rw i o |Wr||||||||l||| ll y 2 l n 4 u 66 4 v 1 T OII I II ||||l|lil|l| u L A M v 0 N F 6 2 F o` u O L x n 3 6 l .l Y 0 6 v R L H o ||II|I|||||I| I I I il i T e u n fd ,6 6 MM2 6 .6 N m 6 N o d N o IIIIIIIIIIII 6I )uw l 6 m SENDER www FIG. 6

.lune 25, 1957 H. REAGAN KEY SENDER TEST CIRCUIT Filed oct. 2a, 1952 12"sneets-sheet 7 wlo' `72o 7 o TTo 75o 76o 'l I I 764./ L

I I I I fl. (+I-#Lim 733 l 763 I Y RN I PULSE START SENDER LEON H. FI'EAGAIII ATTo'RNEY FIG.7-

June 25, 1957 L. H. REAGAN KEY SENDER TEST CIRCUIT 12 Sheets-Sh'eet 8 Filed oct. 28. 1952V 86o ALL g nselsrsns ausv BIO I SENDER' l LEON INVENTOR. H. REAGAN F/Gya.

ATTORNE).l

June 25, 1957 H. REAGAN KEY SENDER TEST CIRCUIT 12 sheets-sheet 11 Filed 001'.. 28, 1952 PICKUP CHAIN FIG. ll

INVENTOR LE'oN H. REAGAN ATTORNEY 12 sheets-Skeet 12 Filed Oct. 28, 1952 COUNTING CHAIN O l 5| l I I l l I l l H 4 .M n w m m 0|| I l l l I l I I l l 1I/AI g 3 D. ..nv|.|.||\ I l I I I I l I||/|||| g g 2 O i 2J- 2 Q 2 m l mil l FIG. I2

FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG. FIG.

INVENTOR.

LEON H. REAGAN v `BY Y g 2 ATTORNEY United States Patent C) KEY SENDER TESZ!` CmCUIT l Leon H. Reagan,Richland;Y Washrfassignor, by'mesne assignments,- to General Dynamics Corporation; acorporation of Delaware Application ;ctob.er 28,1952, SerialNo.' 317,286

19Claimsf- (Cl: 17941175.23)

This invention relates to testing devices for .-usenin connection withV a telephone system register-sender,. the

register-sender being ofthe type Vshown and described. in my copending-application, Serial No.l 311,845, liledvSeptember 27, 1952, now Patent No. 2,730,568.

Most electro-mechanical .telephone equipment. is

adapted to be controlled .by a seriesof directive pulses,

of Which eachseries is representative of a particular digit. These control pulses may be produced by many diierent devices,l such asa conventional telephone dial-.or'by more complicated apparatus, a register-sender, forexample.

Usually, the register-senderis usedwhereatimeis aconhighly desirable to provide a maintenance-.man with equipment of such exibility as to reproduceallconditions encountered in actual practice. This invention is directed toward a testing'` device-and is arranged to be substituted for any operators position. Various schemes of substitution may be provided, suchzas mechanical,

switching,- or the like; however,my testingideviceisprefer.- ably housed in a portablearrangement sov thatzther test equipment may Abe carried .to any register-.senderfwhere a patching cord may be used` to interconnect=the2^test equipment and register-sender..

One object of my inventionis to provide an ,inexpensive testing device for determining the condition of a registersender.

Another object of't-his..invention is to :provides a test device which maysimulate exactly all conditionsfmetby the register-sender in actualfpractice.

Still :another object of-this invention istofprovideaa removable Aconnection .by whichl any register-senderfmay be disconnected from. thefequipment which it normally serves and connected with ytesting-equipment.

A further object of myinvention is to providera .test circuit of such a simple'characteras to make it readily adaptable to portability so that thev test circuit ymay :be carried to any register-sender thereby providing `a simple means for substitution.

A still furtherY object of my invention is to provide means for simulating key set operations of anzintertoll operator position.

Yet another object of my inventiontis to provide means for simulating all features Aof anoutdial trunk circuiti Another object of thisvinvention is to simulatehobk# switch supervision.

Anv additional .obje'ct is to provide a digit indicator which displays a signalindicative ofl 'thel fnurnberf of A"digit pulses which .wereactually.transmitted.;`

Still. anotherr object of this invention is to selectively operate performance lamps which lindicate all sender functions..V

Other objects will be obvious from the accompanying drawings which are designed to teach one skilled in the art when studied-together with the following specification. As in the case of most telephone equipment, the positive terminalfof the-exchange battery may be connected with groundt Throughout the specification and in thedrawing, this` grounded potential is shown by a (-1-) sign While the negative pole-of the battery conveniently may be the -standard 48 volt connection. Thisv is shown in the specication and drawing asa (e) sign.

Fig. 1f shows a block diagram illustrating the manner in which the test equipmentmaybe connected into a standard circuit;

Figs. 2*, 3 and 4, when properly joinedtogether, show latest circuit which may beconnected to a register-sender by means of a patching cord;

Figs..V 5, 6, 7 and 8 show the sender portionl of aregister-sendr;

Figs-..9 and A10 show two register circuits such as may be tested with applicants device;

Figs. 11 -and 12 show a pickup chain and a counting chain which is controlled from theregister circuitl to indicate to the sender circuit how many outgoing digit pulsesare to =be transmitted in each case; andv Fig'.,13` s'howstthe manner in whichFigs. 2-12'are-to ybel joined so that a complete and operative circuit Ais Referring brietiy to Fig. l, there is seen an operators toll'position 10 which-has access to a control shelf 20. The control shelf terminates in a removable connection ,31`that may be any suitable device which is 'adapted to provide a readily interchangeable feature by which various register-senders may be substituted at will.4 For example, connection 31 may be a simple jack-like arrangement. into which a suitable patching cordk 34 may be removably fitted. Patching cordv 34 interconnects control .s'helf 20 withV a register-sender shelf 30 by means of'another removable connection 32 which also may be a simple. jacklike arrangement, for example. Testing equipment 40 is also provided with a patching cord 35a .which'may be substituted for patching cord.34 thereby connecting register-sendery shelf 30 with testing-equipment`40.. J

More specifically, toll position 10 is provided with a cord circuit.12 terminating in a plug 16a which may be inserted into .a jack 16h to answer any incoming call which may have originated eitherin the exchange local to toll position 10 or in a distant exchange. Cord circuit 12" is also provided with a calling plug 17a` which may be'connected with jack 17h to place an outgoing call tofany vdesired point. The'toll operator is provided with dial `circuit.13, position circuitt14 and operators circuit 15 by means of which she may perform any of those functions which are required of an operator. For example, she may operate key set 11-to register any desired digitA indications or 'she may perform certain auxiliary functions; such as controlling the application of automatic'ringing, cancelling registered digits and the like. Keyset 11 operates a register control circuit 21 overV conductors indicated by cable'13 and the register control circuit21in turn extends the keyed indications over cable 22,'A connection 31, patching cord 34, connection 32 and cablef33'to register 38 where an indication is stored whicliis indicative of the digit transmitted by the operatorl'at toll position 10 through the use of her key set 11." This" stored indication serves to controlv counting chain 35 *and vsender 35. Counting chain `ZiStsteps-in Search oftlle-stored digit indication, and on' 'each step sender 36 transmits an outgoing digit impulse over cable 37, connection 32, patching cord 34, connection 31 and cable 23 to cord circuit 12, calling plug 17a and jack 17b.

If a maintenance man should wish to make any test as to the proper functioning of register 38, counting chain 35 and sender 36, he will disconnect patching cord 34-hence toll position 10 and control shelf 20- and substitute therefor testing equipment 40 which now may be connected by means of patching cord 35a, connection 32 and cable 33. Testing equipment 40 is provided with a control key set 41 and a digit key set 42. Digit key set 42 operates a control circuit 43 which simulates the function of register-control circuit 21 while control key set 41 operates testing device 44 to simulate various conditions which may be encountered in actual practice, either at toll position or more remotely from equipment connected to either of the jacks 16h or 17b. Test indicator 45 provides a means by which `a maintenance man may ascertain the results of each test as it is performed.

Figs. 2, 3 and 4, when joined together, teach the operation of testing equipment 40. More specifically, digit keys 200 correspond with digit key set 42 while control keys 201 correspond with control key set 41. Control circuit 43 is shown in detail in Fig. 2. The control keys comprise a talk key which applies a ground marking over contacts 205 for the operation of digit keys 200. An error key provides a means for cancelling at contacts 209 incorrectly registered digits. Position key 202 provides a means by which the maintenance man seizes and operates equipment under test. The ring key is a device by means of which the application or cancellation of automatic ringing may be controlled. The SR key is a sender release key which may be pressed after the registration of all digits as an indication that a particular number has been registered completely. In some cases the SR key may control the transfer of a register-sender so that the operator may have access to either of two register-senders thus providing an idle register-sender at all times. Control keys 201 operate the testing device in Figs. 3 and 4 which correspond with testing device 44. After each test is completed, the maintenance man receives an indication by any suitable means which is shown in Fig. 1 by the block 45 and which is shown in Fig. 3 as lamp bank 340 and in Fig. 4

as lamp bank 462. Patching cord 35a corresponds to` patching cord 400 which connects the test equipment of Figs. 2, 3 and 4 with the sender of Figs. 5 8. Jack terminals 505 correspond with connection 32. The sender of Figs. 5-8 is that shown schematically as element 36 in Fig. l, while the registers of Figs. 9 and l0 are represented by the hollow rectangle 38. 35 is shown in detail in Figs. 1l and 12.

Briefly, the maintenance man substitutes patching cord 35a for patching cord 34 at connection 32 to provide the circuit arrangement shown in Figs. 2-12. After this he operates various keys according to the test which he is about to make. He then operates various selected digit keys 200 causing the control relays of Fig. 2 selectively to mark register conductors R1, R2, R3 and R4 which extend to a register, such as that shown in Fig. 9, for example, where the digit indication is stored. This stored indication results in a particular coded operation of pyramid contacts 901 which functions to transmit a marking over cable 900 to the counting chain of Figs. ll and 12. A pulse source, relays 810 and 820, step the counting chain in search of the marked conductor and simultaneously therewith transmit an outgoing impulse over contacts 821 to the testing device in Figs. 3 and 4. A minor switch is stepped by magnet 450 on receipt of each impulse transmitted from contacts 821, thus leaving brush 461 on a terminal indicative of the number of pulses which have been received. This terminal is lse- Counting chain lectively indicated by one of the lamps in bank 462 which ashes at the end of the test. A proper operation is also indicated by the selective lighting of various lamps in bank 340. Following this, the maintenance man may perform other tests. For example, he may test for stop dial supervision by the operation of one of the keys 330 or 331. A second operation of one of these keys, during any one sending, releases all equipment since it represents a call which has encountered an unstandard condition, such as all equipment busy or a busy called line. The error key in control keys group 201 operates error relay 570 which breaks the register master ground connection at contacts 577 thereby releasing all stored indications. The ring key operates non-ring relay 610 which closes contacts 613 thereby either cancelling automatic ringing or initiating automate ringing, depending upon the position of the RK key and hence contacts 337 and 338. The sender release key SR operates finish register relay 560 which serves to indicate the last registration in a called number. Until this relay releases, any further operation of digit keys 200 is ineffective thus preventing the mutilation of any called number. (If a register-sender transfer feature were provided, the operation of finished register relay 560 would switch the control circuit to the second register-sender after which any further operation of digit keys 200 would result in registering another called number in a circuit which is the duplicate of Figs. 5-12.)

Since patching cord 35a has negligible resistance with respect to that of the oce cabling including items 34, 31, 22 and 21, means must be provided for simulating the intra-oflice cabling in the test device. For this purpose, I provide a resistance R200 connected to contact 211. This resistance may be either an average selected to match most olce conditions, or it might be made adjustable where a wide variation is encountered in actual practice.

It is thought that a clear understanding of applicants invention will be facilitated by a detailed description of the step-by-step operations required in each test.

Register-sender seized After completing a connection between the test equipment and the register-sender under test, the maintenance man will seize that register-sender in much the same manner as an operator would. For this purpose, he operates position key 202 thereby extending a grounded over an obvious circuit including contacts 203, taking ground conductor TG and master ground conductor MG in Fig. 4, and through the windings of ground relay 510 to battery. Relay 510 operates to apply master ground to the register-sender circuit by way of contacts 512, register master ground conductor RMG and also by way of contacts S12 and 577 to another register master ground conductor RMG. Practically all equipment in the register-sender circuits operate from one of these master ground leads; therefore, among other things, position key 202 provides the maintenance man with a simple method of returning everything to normal. Contacts 203 on position key 202 also closes an obvious circuit to slow-operate position take relay 320 which is arranged so that it does not open its contacts until the expiration of a brief interval of time after contacts 203 close. During this brief interval of time position key 202 completes a circuit to seize the register-sender by operating allot register relay 910 over a circuit which may be traced from grounded on contacts 203, lthrough normal contacts 321 of the not yet operated position take relay, over register take conductor RT, and through the winding of allot register relay 910 to battery. Allot register relay 910 operates and locks over a circuit which may be traced from battery through the winding of allot register relay 910,

atomes normal contacts 921, operated contacts 916, to register master ground conductor RMG by way of normal contacts 577 and operated contacts 512. Groundedf(l) on close contacts 203 also is extended over normal contacts 322 of the not yet operated position take relay and marker take conductor MT to battery by way of allot marking relay 970 in the first register. Allot marking relay 970 operates and locks by Way of its contacts 972 and operated contacts 917 of allot register relay 910 to register master ground 500 as traced above. After an interval of time sufficient to permit relays 910 and 970 to operate and lock, positiontake relay 320 operates to open contacts 321 and 322'.

If the testing is to have any value whatsoever, it is necessary to notify the maintenance man step-by-step of each operation throughout the entire testing procedure from start to finish. For this purpose, means is provided-for signaling each operation. In the embodiment of my invention shown in the drawings, means is in the form of lamp bank 340; obviously, however, other signal means could be substituted therefor. Since one operation has been completed, i. e., equipment has been seized, it is necessary to notify the maintenance man of this fact. More specifically, position key 202 closes a circuit for lighting non-key lamp 348 and operating lamp relay 210 as an indication that no digit key is to be operated at this time. The operating circuit may be traced from battery through the lament of nonkey lamp 343, closed contacts 204, the winding of lamp relay 210, and over non-key conductor NK to closed contacts 862 of all register busy relay 860. Relay 860 is slow-to-operate and therefore contacts 862 are closed at this time. The circuit may be further traced to grounded 500 by way of register master ground conductor RMG and contacts 512 of ground relay 510. Lamp relay 210 operates to remove ground from the various register leads at contacts 211. This is to prevent a false registration in case the operator should attempt to actuate one of the digit keys before subsequent equipmentl is ready to receive a registration. That is, lamp relay 210 opens contacts 211 thereby removing a grounded from contacts 221, 231, l241 and 251. If the operator actuates any digit key, at least one of thefcontrol relays, 220 for example, operates to attract armature 221 which, however, is ineffective since contacts 211 are open. The resistance R200 simulates the resistance `encountered in intra-oiice cabling.

When position key 202 is operated, transfer lamp 346 lights over a circuit which may be traced from grounded at contact 203, conductor TG, through rest contacts 567, conductor TL and through lamp 346 to battery. This lamp serves no useful purpose at this time.

After a brief interval of time the register-sender is ready to receive and store information indicative of a particulardigit. The maintenance man is notified of this fact by non-key lamp 348 which goes out. This brief interval is measured by the slow-operate time-interval `of all register busy relay 860; therefore, relay 360 now operates over a circuit including contacts 926 and in parallel therewith, contacts 1026, to grounded 500 by way of register master ground conductor RMG and closed contacts 512. Responsive thereto, contacts S62 open thereby removing grounded (l-) from the NK lead thus releasing lamp relay 210 and extinguishing non-key lamp 348. Lamp relay 210 closes contacts 211 thereby extending grounded to contacts of control relays 220-250- Register-sender test The maintenance man sees lamp-348 go out and recognizes this as a signal that he may proceed to actuate 'the digit keys, if he'so desires. Prior thereto, he will selectively operate various keys depending upon which test-he desires-to conduct.A Assuming that the lirst test is merely to test the general operation of the registersender, the maintenance man proceeds by operating the talk key of controlkey group 201 to close contacts 205 thereby extending a grounded marking to each ofthe digit keys. Trunk key 332 must Valso be operated to complete a circuit for loop lamp 345 by way of contacts '334' as an indication that the circuit simulates a completed connection to'the trunk circuit. In this case the simulated trunk comprises pulsing conductor PL which represents the usual ring conductor and by off-normalc'onductor ON-which represents the usual tip conductor. Pulsing contacts 821, found in Fig.` 8, provides a connection to grounded on contacts 621 by means of which ground pulses may be transmitted over conductor PL into the test device. Contacts 336 of Itrunk key 332 prepare a circuit for pulsing relay 410 which isnot immediately effective while contacts 335 prepare a circuit for ofi-normal relay S60-Which is not operated at this time since its circuit is now open at contacts 312'.I

The circuit is now in condition for transmitting directive control pulses; therefore, the maintenance man may proceed by actuating any desired one of the digit keys responsive to which either one or two of the control relays 220, 230, 240, and 250 operates to close. its or their lowermost contacts thereby selectively marking the register conductors R1, R2, R3 or R4. The purpose of markings on these R conductors is to control register relays in either Fig. 9 or Fig. l0 thereby completing a path for the registration of a condition indicative of which key was operated.

For `the sake of explanation, it may be assumed that the key rst operated is digit key 8. Upon inspection of this key it will be seen that contacts 206 close a circuit for the operation of control relay 240 over a path which may be traced from grounded through closed contacts 20S, 208 and 206 through the winding of relay 240 to battery. Contacts 207 close a circuit from grounded at contacts 205 which may be traced through the winding of control relay 230 to battery. Each of these control relays operates to close its lowermost contacts 231 and 241 thereby extending a marking grounded applied at armature 211 to the conductors R2 and R3. .Control relays 230 and 240 also operate contacts 232-and 242 thereby closing a circuit extending from grounded at contacts 203, through operated contacts 232 and 242 in parallel, to the hold ground conductor HG which serves to extend a temporary holding ground for the particular register in which the digit is to be stored. At contacts 233 and 243, control relays 230 and 240 open the loop connecting conductors PUR and PUF, thereby removing grounded (l) 500 which was formerly extended over operated contacts 512, rest contacts 577 and conductor PUR to conductor PUF.

it is necessary to store an indication of the keyed digit 8 so that other digits may be keyed without having to wait for the transmission of a complete train of digit pulses. First, the register of Fig. 9 is assigned. Then, various register relays operate depending upon the digit key that was pressed after which that register locks under the influence of a register hold relay until the sender completes the transmission of the digit pulse train representing the stored digit. Responsive to the completion of such transmission, the register is unlocked and marked idle for further storing digits. Meanwhile, succeeding digits are stored in other registers as fast as they are keyed. More specifically, the grounded applied by way of closed contacts 203, 232 and 242 to the vHG lead serves to lock allot register relay 910 operated by way of contacts 915 (it previously operated before slow-operate relay 320 opened contacts 521), thereby closing contacts 5911-914 to connect the of Fig. l).

iirst register relays 930, 940, 950 and 960 to register conductors R1, R2, R3 and R4, respectively. Thus, re-

lays 940 and 950 are operated over conductors R2 and R3 from contacts 231 and 241 of the control relays. Contacts 943 and 953 close to operate register hold relay 920, which operates to open contacts 921 thereby ,breaking one of the holding paths for allot register relay 910.

After a brief interval of time, the maintenance man releases digit key 8 thereby opening contacts 206 and 207, thus releasing control relays 230 and 240, opening Vcontacts 232 and 242, to remove grounded (-1-) on closed contacts 203 from holding conductor HG. Allot .register relay 910 releases.

,about which more will be said later in the section headed Register Release.

Assignment of next register The iirst digit is completely registered at this time and therefore it is necessary to assign the next register (that For this purpose, register hold relay 920 (operated responsive to the closing of contacts 943 and 953) closes `contacts 924 thereby completing a circu-it for the operation of allot register relay 1010 as an indication that register relays 1030, 1040, 1050 and 1060 are next to be used. This circuit may be ltraced from battery through the winding of :allot register relay 1010, rest lcontacts 1021 and 1022, operated contacts 924 to conductor PUF which extends to Fig. 2 where contacts 233 and 243 have just closed responsive to the release of digit key 8, thereby connecting conductors PUF` Iand PUR which lfurther extends the connection by way `of closed contacts 577 and 512 4to grounded (-1-) 500. A'llot register relay 1010 operates thereby closing contacts 1011, 1012, 1013 and 1014, thus assigning register relays 1030, 1040, 1050 and 1060. Relay 920 also `opens contacts 926 and closes contacts 925 thereby removing one connection to all register `busy relay 86) which previously extended through contacts 926 and register master `ground conductor RMG to grounded (-1-) 500 by way of closed contacts 512; however, all register busy relay 860 does not release at this time since another holding circuit is completed by way of closed contacts 1026 (the register of Fig. l0 being then idle).

Sending the stored digit Since the digit indication is completely stored, the register of Fig. 9 now is in condition to -control the transmission of a .train of impulses representative of the stored markings. However, before the actual ypulse train is transmitted it is necessary to prepare the sender.

More in detail, `an ofi-normal condition is created to signal the sender when register hold relay 920 closes contacts 925 for extending register master 4ground conductor RMG and therefore grounded (-1-) 500, connected through operated contacts 512, to :the winding of main start relay 530 and battery. Relay 530 operates thereby closing contacts 531, thus extending grounded (-1-) over conductor PU to [pickup lamp 342 and dialing relay 310 to battery. Dialing relay 310 operates to simulate the operation of a dialing relay in an operator cord circuit. rIhe dialing relay of a cord circuit normally associates ltha-t particular cord circuit which is individual to a call with the dial circuit which isl common to many cord circuitsthus preparing a signal path which extends .from the register-sender to the particular cord' circuit over which the call is to be extended. Pickup lamp 342 lights as an indication that the circuit has in fact been so extended. In operating, dialing relay 310 connects grounded (-1) through closed contacts 311, 330 and 331 to the ST lead and supervisory relay 710. At contacts 312, dialing relay 310 completes a circuit closing conductor ON for operating off-normal relays 360 and 520, the circuit lbeing traced from grounded through the winding of relay 360, operated contacts 335 and 312, the ON conductor, through resting contacts 623, 653 Iand operated contacts 511 to battery through the winding of off-normal relay 520. Supervisory relay 710 closes its contacts 712 thereby extending grounded (-1) over the SR conductor to light supervisory lamp 349 as an indication of the extent to which the sending operation has developed this far. Relay 360 operates and prepares a circuit for pulsing relay 410 and for a second off-normal relay 370. The otnormal relay 520 also operates in series with relay 360 thereby closing contacts 521 to complete an obvious circuit for the operation of still another off-normal relay 630.

Since dialing relay 310 picked up as simulated from a cord circuit, it now is necessary to hold that relay from the register-sender to maintain connection between the register-sender and the cord circuit. For this purpose relay 630 closes contacts 631 to extend a grounded (1-) over the H conductor and through the iilarnent of hold lamp 341 to dialing relay 310. Lamp 341 lights as an indication that the register-sender will in fact hold the dial circuit. Relay 630 also breaks the pickup conductor at contacts 632 extinguishing lamp 342; however, there is no danger of dialing relay 310 releasing at this time since contacts 631 are X contacts which close before contacts 632 open. Relay 630 also closes contacts 637 completing a circuit for lighting sending lamp 347 as an indication that the register-sender is now ready to send outgoing pulses. The 4circuit for `lamp 347 may be traced from battery through the filament of sending `lamp over the SL lead, through contacts 637 to grounded (1) on 'contacts 853.

Y Before the individual outgoing impulses may be sent, it `is necessary to start pulsing relays 810 and 320 which serve to step a count-ing chain and simultaneously therewith to transmit outgoing pulses. That is on each step of the counting chain, a test is made to determine whether that step completes the digit pulse train, if not a further step is taken and another outgoing impulse is transmitted. This process is repeated until the entire pulse train is completed.

In detail, the pulse source is started by the energization of relay 810. It will be recalled that allot marking relay 970 operated from grounded (-1-) on contact 203 for the brief interval required for the slow-operate position take relay 320 to open contacts 322, after which allot marking relay 970 locked to register master ground conductor RMG by way of contacts 972 and 917. Relay 970 also closed contacts 974 thereby completing a circuit to operate pulse start relay 750 over the path including closed contacts 974, conductor RR, contacts 742, the winding of low resistance relay 750, a register master ground conductor RMG', closed contacts 577 and 512 to grounded 500. Pulse start relay 750 operates to close its contacts 751 =thereby operating the high resistance pulse start relay 760 which in turn closes its contacts 763 thereby completing a path to pulse source relay 810 over the circuit which may `be traced from battery through the 'lower winding of relay 810, a potentiometer, and contacts 811, 763, and 646 to grounded (-1-). Pulsirrg relay 320 yalso operates over the circuit including contacts 646, 763 and 836. It will be noted that a grounded (-1) is now applied to each side of capacitor C800 'causing it to discharge; it previously had been charged over the upper winding of relay 810, a potentiometer and the lowermost Windingof relay 810.` For afbrief interval of time, capacitor-C800 is dischargng.- Thisdischarging currentdilerentially'energizes relay 810, preventing its operation. When .a suicient charge has leaked o capacitor C800,1acco:rding to the setting of rthe potentiometer, current in an energizing circ-uit including the lower -winding of relay 810,-contacts 811, 763 yand 646 is -sutii'cient to operate relayI S-which attracts anmaturell, thereby breaking its .own energizing circuit. Capacitor C800 is nowy charging .over a circuit from battery through the-lower winding. of relay 810, the potentiometer, the upper 4winding of relay 810, capacitor C800, to grounded (-l-). lFor a brief-interval lof time, .this charging current is sufficient to hold-relay S110 after which time the charge onfcapacitor C800 is lbuilt to a sufficient leVeL-and the charging current ends (contacts 311 4being -then open) causingrelay 810 to release. This process is repeated .continuously as long `as contacts 763 remain closed. On each oper-ation land release, pulse lgenerating relay 310 opens and #closes contacts `812. thereby pulsing relay 820 `over a path which may Vbe traced frombattery, through the winding of relay 820 and contacts 837, 312 and 647 to grounded (-|-)-contacts 7-14 are open at ,this time. Each -time that relay 820 is pulsed under the inuence of contact 812,: various contacts are opened or lclosed to control-the :oper-ation of the counting chain -in Figs. ll and-12 or to transmitting an outgoing impulse at contact 821.

Once pulsing relays 810 and 820 are running, the counting chain. (Figs. 1l and l2) is stepped simultaneously with the transmission of outgoing pulses to count to the number which was keyed. The rst closure of contacts 825 by pulsing relay 820 completes a circuit for the operation of release delay relay S30 over a path which may be traced from battery through the winding of relay 830, closed contacts 834, 746 and 825 to register master ground vlead RMG, contacts 577 and 512. to grounded 500. Release delay relay 830 operates and locks over the path from battery through the winding of relay 830, cl-osed contacts S33, 643 and 747 to register master ground conductor RMG'. On operation, release delay relay 830 closes its contacts 831 thereby extending grounded on register master ground conductor RMG to contacts 1263, 1253, 1243, 1233, 1213, 1173,' 1163,1153, 1143, 1132 and 1123 through the winding of pickup chain relay 1110 to battery. This relay oper-` ates and attracts its armature 1114, locking to the CB conductor and contacts-826 which close when relay 320 next releases responsive to the operation of relay-810.

Once relay 1110 operates, relays of the pickup chain and the counting chain are sequentially operated in a stepby-step fashion in search of a marked conductor in cable 900. Thatis, pickup chain relay 1110 operates contacts 1116 thereby connectingl the CA conductor to the second pickup chain relay 1120. The next time that pulsing relay 820 releases, it completes a circuit from register master ground conductor RMG through closed contacts 823 and 832 to the CA conductor, and closed contacts 1116 to battery through the winding of relay 1120. This -relay opens contacts 1123 thereby breaking the original operating circuit for the irst pickup chain relay 1110 which continues to hold over contacts 1114 and the CB conductor to contacts 826, 835 and 647 to grounded When relay 820 next operates to remove grounded at contacts 326, relay 1110 releases` to close contacts 1117. It will be noted that contacts 1126 are now closed since relay 1120 holds by way of contacts 1122, 1132, 1143, 1153, 1163, 1173, 1213, 1223, 1233, 1243, 1253, 1263 and 331 and register master ground lead RMG to grounded 500 by way of contacts 577 and 512." In a similar manner, each lof the relays in the pickup chain and the counting chain controls therelease of .the next preceding. relay and prepares the` next succeeding relay which will operate on the next release of pulsing relay 820.

When relay 1130 operates at the 4end of the pickup chain, contacts 1133 closeas an indication that thenext relay to operate in the counting chain represents the digit 1. The net result is that dial start relay 840 .operates over the path from battery through the lower windings of relay 840, contacts 1133,745 and 824 to register master groundv conductor RMG'. Relay 840 locks over contacts 843 and831 to register master ground conductor RMG'. Contacts 841 open to put vthe PL conductor under the control of pulsing-relay 820 at contacts 821. Contacts 842 close to extend a grounded (--l-) marking to pyramid contacts 901 by Way of contacts 971, while contacts 844 operate a second dial start relay S50.

Relay 820 continues pulsing to transmit the proper number of outgoing digit pulses, opening contacts 321 on each impulse. Pulsing relay 410 operates over contacts 365, 336 and pulsing conductor PL through contacts 821, 571 and 621 to grounded Pulsing relay 410 closes contacts-412 thereby operating off-normal relay 370 over the circuit including grounded (-lthe winding of relay 370, contacts 412, 363, 335, 312 and the offnormal conductorON to battery by way of contacts 623, 653, 511 andthe Winding of off-normal relay 520. Relay 370 operates and locks at its contacts 372 to the off-normal conductor ON over the operating path just described. Responsive thereto-contacts 371 open; however the loop -lamp does not go out since another circuit for lighting loop lamp 345 is completed over the path which may be traced through contact 334 to grounded (-I-V) on closed contacts 411; thus, lamp 345 ashes on each pulse. This is an indication that the outgoing pulses from contacts 821 are actu-ally being transmitted into the trunk. Otherwise, it may be possible for everything to be functioning perfectly and yet contacts (S21, for example) may be dirty, or for some other reason, the outgoing pulses never reach the trunk. Pulsing relay 410 closes contacts 413. which are part of a path for operating stepping switch magnet 450. Operation of contacts 414 completes a circuit from grounded (-l) through closed contacts 366 and 414 to operate release delay relay 420 vwhich in turn closes its contacts 421-. These are not eective at this time; howeverthey prepare a circuit for shunt relay 430. A brief time interval later pulsing relay 410 Vreleases responsive to the release of pulsing relay S20 opening its contacts 821- and thus transmitting the first outgoingpulse. Relay 410opens contacts 414 and closes contacts 415. A circuit is now closed to operate shunt relay 430 via contacts 366, 415 Vand 421. Shunt relay 430 closes contacts 432 to operate a second shunt relay 440 and also closes contacts 433 to prepare a path for operating stepping magnet 450; however, magnet 450 does not operate at this time since contacts 413 are now open. Shortly thereafter pulsing relay 820 reoperates to close contacts 821 thereby reoperating pulsing relay 410 which closes contacts 413 to operate stepping 4magnet 450 once, thus moving brush 461 once as an indicationthat one pulse has been received. Relays 420, 430 and 440l hold operated throughout pulsing due to their slow release characteristics. 'Ihe process repeats on each pulse from relay S20-leaving brush 461 standingl on a Contact which is representative of the number of pulses in the outgoing pulse train just transmitted.

Returning for the moment to the register of Fig. 9, it controls the sender `circuit to determine the number of outgoing impulses. Briefly, one digit marking conductor is at grounded (-1-) potential and this marking is extended over cable 900 to the counting chain. When the marking is reached, pulsing relays 810 and 820 are disabled to end` the outgoing digit pulse train. More specically, allot marking relay 970 is operated at this time thereby closing contacts 971 as an indication that the marking stored in the first register (Fig. 9) is the first to be operative for controlling the counting chain, Figs. 1l and 12. Since it was assumed that the digit 8 was registeredrelays 950iaud 940 are locked operated; therefore, it is possible to trace the circuit from grounded 1 l (-1-) on contact 842 through contacts 971, 931, 941'and 951 to conductor 8 of the digit marking cable 900. This rmarking is extended over cable 900 to Fig. 12 where conductor 8 is at grounded (-1-) potential. f

In the counting chain of Figs. 11 and 12 each relay controls the release of the preceding relay and prepares a circuit for operating the next relay. Following the operation of relay 1130, the resulting closure of contacts -1133 is an indication that the next pulse is the irst outgoing impulse in the train of digit pulse, relay 1140 operates responsive to the next release of pulse relay 820. That is, contacts 823 close to complete a circuit which 4may be traced as follows: from battery through the winding of relay 1140, closed contacts 1136, 1127, 1117, conductor CA, contacts 832 and 823, to the register master ground conductor RMG and through contacts 577 and 512 to grounded (-1-) 500. Relay 1140 operates to open contacts 1143 over which relay 1130 has been holding. Relay 1130 continues to hold over contacts 1134 and conductor CB until the next operation of pulsing relay 820 opens contacts 826 to release relay 1130 thereby opening contacts 1136 and closing contacts 1137. Meanwhile, relay 1140 holds over a circuit which may be traced from battery through the Winding of relay 1140, contacts 1142, 1153, 1163, 1173, 1213, 1223, 1233, 1243, 1253, 1263 and 831 to register master ground conductor RMG. Nothing further happens at this time since there is no marking on digit marking conductor 1 of cable 900. An attempt to trace this conductor through pyramid contacts 901 reaches open contacts 932. A short time later, relay 820 releases closing contacts 823 and 826 thereby stepping the counting chain one step further. That is, a circuit is now closed for relay 1150 over a path which may be traced from battery through the winding of relay 1150, closed contacts 1146, 1137, 1127, 1117 and over conductor CA through closed contacts 832 and 823 to register master ground conductor RMG Iand contacts 577 and 512 and grounded 500. Relay 1150 operates to open contacts 1153 thereby releasing one holding circuit for relay 1140, and relay 1150 locks to register master ground conductor RMG' by way of contacts 1152, 1163, etc., 831 and 823.

The counting chain continues this step-by-step operation. As it operates, each relay in the counting chain completes a circuit to the marking conductor MK. In the case of each of the conductors 1 7 nothing happens since the circuit from marking relay 740 may be traced back to pyramid contacts 901 where an open condition is found. It may also be recalled that pulsing relay 820 transmits an outgoing pulse at contacts 821 corresponding to each of the digit marking conductors 1 7.

This process continues, the counting chain being stepped one step for each operation of pulsing relay 820 until digit marking conductor 8 is reached, at which time a circuit is completed for the operation of marking relay 740 to indicate the end of outgoing impulses transmitted at contacts 821, eight impulses having been transmitted. This circuit may be traced from battery through the winding of marking relay 740 and contacts 822, over marking conductor MK to contacts 1241, digit marking conductor 8, cable 900, pyramid contacts 901, closed contacts 951, 941, 931, 971 and 342 to grounded (-1-). Marking relay 740 operates to close contacts 741 and lock to a grounded (-1-) extended from contacts 851. At contacts 742, the marking relay opens the register hold circuit through low resistance relay 750 which releases, and .at contacts 743, closes the register hold circuit through contacts 762 to grounded (-1) by way of the lower winding of high resistance relay 760. Contacts 743 may be arranged to close before either of the contacts 744 or 742 open.

Release of register The sending function being now complete, the register of Fig. 9 must be released while the sender isV held immobile to prevent the transmission of any false impulses. It will be recalled that register relays 940 and 950 had previously locked to conductor RR by way of contacts 942 or 952 in series with contacts 974. The register relays are marginal and will hold in series with the low resistance of relay 750 which is normally connected to conductor RR but will release when held in series with high resistance relay 760. Therefore, register relays 940 and 950 release responsive to the shifting of register hold conductor RR from low resistance relay 750 to high resistance relay 760 by means of contacts 742 and 743, thereby opening the circuit at contacts 942 and 952 over which high resistance relay 760 was held, this circuit being traced over contacts 762, 743, 974, 942 and 952 in parallel, to battery through the windings of relays 940 and 950. High resistance relay 760 releases. In releasing, relays 940 and 950 open contacts 943 and 953 causing register hold relay 920 to drop. When relay 760 releases, contacts 763 and 764 open to disable pulsing relays 810 and 820. During this interval, relay 820 has been held operated by marking relay 740 to insure the fact that no further impulses will be transmitted, the holding path being battery, the winding of pulsing relay S20, contacts 749 and 844 to grounded (-1-) on register master ground conductor RMG. Marking relay 740 opens three holding circuits for release delay relay 830 at contacts 746, 747 and 745. Release delay relay 830 drops to open contacts 331 in the holding circuit of dial start relay 840, releasing this relay, thereby opening contacts 844 over which the second dial start relay 850 was held causing it to release.

Pulsing relay 820 falls since all of its holding circuits are now open. That is, contacts 844 open responsive to the release of dial start relay 840, contacts 837 are open due to the release of release delay relay 830, and

contacts 763 are open due tothe release of high resistance relay 760. Marking relay 740 falls since contacts 822 open responsive to the release of relay 820 and since contacts 851 opened responsive to the release of second dial start relay 850. Matin start relay 530 drops responsive to the opening of contacts 747a.

Returning to the operation of the counting chain, it will be recalled that each of the Irelays operated and locked depending upon the next relay for its unlocking and release. Since relay 1240 operates last in the case supposed-the digit S- it remains locked over contacts 1242 and 1244-; therefore, to return the counting chain to normal, it is necessary to open both of these holding circuits at this time. The circuit from contacts 1242 extend to contacts 1253 and 1263 to contacts 831 which are now open since release delay relay 830 has fallen. The second holding path extending from contacts 1244 is by way of contacts 1235, 1225, 1215, 1175, 1165, 1155, 1145, 1135, 1125, and 1115 to the CB conductor and contacts 826 which are now open. Thus, the counting chain is returned to normal.

Digit test The purpose of stepping brushes 461 in synchronism with pulsing relay 820 is to determine, by test, how many outgoing pulses are actually transmitted land whether all of these pulses are suitable for stepping a switch. At this time, it may be well to review, briefly, the manner in which this test has been set up by the operations just described.

Since it was assumed that the maintenance man operated digit key 8, digit marking conductor 8 was connected to grounded (-1) on contact 842, which marking was then extended over cable 900 to digit marking conductor 8 at contacts 1241 of relay 1240 in the counting chain of'Fig. l2. The counting chain was operated stepby-step until it reached this marking, at which time a circuit was completed over the marking conductor MK to operate marking relay 740, which closed contacts 749 to hold pulsing relay 820 operated over a circuit including atomes contacts 844, register masterground. cOnductorRMG., contacts 577 and 5,12V to -grounded 500.- 'Phisheld the pulsing relay 820 operatedgso that it could not transmit further pulses at contact S21. Thus,pulsing relay 410 received eight pulses .responsive to which stepping magnet 450v operated brushes461to theeighthposition thereby completing a circuitl for thev eighth lamp in the counting lamp bank462.

The paragraph labove reviews the .operation Whichset up thetest` conditions. Following-thisthe results of the testare `given when a circuit is `completed to llash lamp 8 in bank 4.62 as .an indicationthateight digit pulses were actually received. More specifically, when relay i 820 holds at the 4end of the pulse train,.pulsing relay410 in turn holds its .contacts 415open'1and contacts 414 closed, thus completinga circuit for holding release delay relay 420 operated and for releasing shunt relay 430 which drops shortly to open the holding path of a second shunt relay 440l at contacts. 432 while closing contact 431 vthereby completing a circuitby way. Yof contacts 431 and 441 to common terminal 464 of the minor switch. (Contacts 441 remain `Closed during Athe slow release time I.interval of relay v440.) Since wipers 461 have been stepped to t-he eighth position, a circuitis completed from contact 464by way of shorting Wiper 461 and lamp `8 to batter-y 465.l After a brief interval of time determined by its slow release characteristics, rrelay 440 releases closingcontacts 442 :and opening contacts, 441, thereby ex- `tinguishing the lamp which was lit. This ash of lamp 8 indicates Vto thevmalntenance man the number of digit pulses which ,were transmitted by pulsing contacts 821. of pulse relay 820. When relay 440 closed its contacts 442a circuit Ais completed for operating release magnet 460 to returnthe minor switch to normal, the lcircuit being by way of contacts 431, 442 and minor switch olinormal contacts 463. 4 Upon reaching normal, off-normal contacts 463 open to cause release magnet 460 to drop. The maintenance. man may now proceed to key further digits, thereby testing the register, counting chain and sender under various conditions.

All registers busy and supervision test The lmaintenance man may now` conduct a test to determine whether proper supervision is returnedwhen .all registers. arelilled. By Way of explanation, it may be well to review how the registers are assigned, as was explained above under the heading Assignment of Next Register. The first digit is stored in the register `of Fig. 9, this register being assigned by the operation of register allot -relay 910 which, attracted armatures911-914 .thereby completing a connection from the first register relays 930, 940, 950 and 960 to conductors R1, R2, R3 and R4. After the first digit is registered, register hold relay 920 operatesto Vclose contacts 924 thereby causing allot register relay 1010 -to operate over ta path which includes contacts-1021, 1022-,.924, conductor PUF, contacts 223, 233, 243, and 253, conductor PUR, contacts-577 and 512 `to grounded (-1-) 500. Allot register relay 1010 closes its contacts 1011-1014 thereby connecting the last register relays 1030, 1040, 1050 and 1060 to control conductors R1, R2, R3 and R4, respectively.

The maintenance man operates any digit key which he may desire causing various control relays of Fig. 2 to operate in combination. The subsequent lfunctions are substantially the same .as those described above in connection withthe register of Fig. 9; however, if the sender has not yet transmitted pulses 4representative of the digit stored in the register of. Fig. 9, then bothV registers are busy and further keying must be postponed.

Normally, it is contemplated that the first register Will be idle'before the last register is filled completely. In

such a case, register hold relay 1020 closes contacts 1024 thereby operating allot register relay 910 over a path includingcontactsf921, 922, 1024, conductor PUF, contacts 223,233, 243, 253, conductor'PUR, contacts 577V and 512.3' to grounded.(+).500, .thus reassigning the register ot Fig. 9. Meanwhile allot marking relay 97 0 releaseswhen register hold relay: 920 4opens contacts 923.v It will be recalled that theregister holdrelay is released responsive to the complete. transmission of an outgoing pulse train by the `sender circuit. Allot.markingrelay 970 releases contacts 9.75 thereby opening the circuit by which a second allotmarking relay 9.80..has been held operated; however, this relay continues to hold briefly during its slow release period'. Relay 970a'lso closes contacts 976 for extending grounded fromregister master ground conductor RMCiy over, contacts-876iand 981 to allot marking relay 1070cwhichoperates and locks over contacts 1072 during the slowy release time of relay 980, after which the original operating circuit for relay 1 070v is. opened at contacts 981. A second allot marking relay 1080 operates when relay 1070 closes contacts 1075. Allot marking relay 1070 then closes contacts 1071-for applying grounded (-1-) on contact` 842 to pyramidcontacts 1000. Thus, the counting chain once more. will, be directed through its chain of operations in Search of the digit marking conductor extending. the grounded. (-1-) from contacts 842 through pyramidcontacts1000, over. cable 900 to register relay contacts such as.1141for example. After a digit pulse train representingithe digit stored in Fig. 10 is completed, registenhold relay 1020.1'eleases-in the same manner as did. register hold-relay- 920-thereby opening contacts 1023 to release.V allot marking relayy 1070 which had been holdingzoperated-at contact 1072. This reoperates allot marking relay 9.70, during the slow release interval of relay 10.8.0 by way. of contacts 1076. and 1084 in much the same mannerV as described above when; relay 1070 originally operated during the slow-release time of relay 980.

In. some `cases,.the.,operator may. key digits too fastor for some other reason the registers may not be emptied as anticipated-inwhich case an all register busy condition is encounteredandthe operator must be so informed. That is to say, if the operator were permitted to key further digits, these keyngs would be ineffective since no register is then. availablefonstoring the information. She must be aware of .thisfacu therefore a lamp lights at her positi-onand the vmarking path for register conductors R1, R2, R3 and R4.is.opened. i

It is desirable. to .provide a maintenance man with means for testing to determine whether the operator would infact receive a proper all register busy supervision and to determinewhether further digit keys would in truth 'be inelective.. To initiate. this test, the maintenance man lirstmust produce an all register busy condition. Hemay-.do thisby disablingthe sender =by any desired means. For example, he may operate one of the supervisor-y Vkeys 330. or 331 thereby releasing relay 710 which -in turn closes. contacts 714 to complete a circuit via contacts845, 714, 764 and 837 to hold pulsing relay 820 operated.. -This prevents the transmission of any outgoing-digit lpulses. until the supervisory key is released to reoperate relay 710. While one of the supervisory, keys 330 or 331V is so thrown, the maintenance man proceeds .tov key enough digits to till all available registers. Assuming this to be the case, both. of thev register holdrelays 920 and 1020 are operated thereby opening contacts 926 and 1026. Since the multiple holding paths for all registers busy relay 860 are now open, this relay releases nto close contacts 861 and 862. It will be recalled that each` of lthe control relays is provided with a Contact such as 233 and 243 for `disconnecting grounded 500 -fromvconductor PUF-it previously had been extended lby way of contacts 512, 577 and conduct-or PUR. Wheny all registers busy relay 860 closes contacts 861, grounded 500 is connected directly to conductor PUF over a circuit including register master groundconductor RMG, contacts 577 and 512. After the all registersV busy condition has ceased, for example the register of Fig. 9 becomes idle, it is necessary to cause that register to be assigned as the next to receive and store a digit. For this purpose grounded (-1-) 500 is connected `via contacts 512 and 577 to conductor RMG and on through contacts 861, 1024, 922, 921 to battery through the winding of allot register relay 910 which operates to close contacts 911-914 thereby assigning the register of Fig. 9. Contacts 862 complete la circuit from grounded 500 through operated contacts 512 to register master ground conductor RMG, through contacts 862, the NK conductor, lamp relay winding 210 and close contacts 204 to non-key lamp 348. The lamp lights as an indication that the operator may not key any further digits; furthermore, lamp relay 210 operates and opens contact 211 thereby removing grounded from register conductors R1, R2, R3 and R4, thus further preventing the registration of any further digits at this time. This indicates to the maintenance man the fact that an all register busy condition returns the proper supervision.

Error test Very often the operator may make a mistake and depress the wrong digit key, or for some other reason, she may wish to cancel digits which have been stored. For this purpose, she is provided with an error key which releases all equipment. The test man may simulate this by depressing his error key whereby he releases all equipment. Contacts 208 open to remove the grounded connection which previously had been extended to the digit keys from contacts 205. This prevents the registration of any further digits While an erroneous registration is being canceled. Operation of the error key also closes contacts 209 thereby extending grounded (-i-) on contacts 205 over the error conductor ER through contacts 565 and the winding of error relay S70-which operatesto battery. It will be recalled that the master ground for the register and sender circuits extends from grounded (-1-) 500 on contact 512, through rest contacts 577 to hold or operate almost all of the equipment in the register and the sender circuits as well as in the counting chain. The removal of this ground by the operation of contacts 577 causes all such equipment to be released. For example, if a digit were registered in Fig. 9 causing relay 940 to be held operated by way of contacts 974, conductor RR, contacts 742, the winding of low resistance relay 750 to grounded on conductor RMG, this relay would drop since its holding circuit further extends from register master ground conductor RMG' to contacts 577 which are now open. Formerly, the circuit continued through contacts 577 and 512 to grounded 500. In a similar manner, the holding path for most of the equipment may be traced back to contacts 577 and found to be released upon operation of error relay 570.

It is also necessary to prevent the transmission of any further outgoing impulses when an error condition is indicated. For this purpose, the error relay opens contacts 571 thereby removing grounded (-l-) from the PL conductor to prevent the transmission of any more outgoing impulses. This also releases pulsingV relay 410 which opens contacts 411 to extinguish loop lamp 345 as an indication that a switch train would be released. In this case loop lamp 345 relights when the error relay reoperates responsive to a return ofthe error key to normal.

Means is also provided for releasing special equipment upon the operationV of the error key. For example, if the operator desired to prevent automatic ringing she would have operated the ring key (see the section entitled, Sender Release Without Ringing) in the group of control keys 201, therebyl extending a circuit which may be traced from grounded (-1-) on contacts 205 through contacts 208 and operated contacts of the ring key, over the NR conductor and through contacts 561, 641 and 612 to battery by Way of the winding of non-ring relay 610. This relay then would have operated and locked by way of contacts 611 and 572 to the hold conductor H. In operating, the error relay `opens contacts 572 thereby releasing this circuit.

' Means is provided to simulate the operation of position V"le take relay 320 upon release of the error key. This is necssary since the assigned register is released by error relay 570 and since position take relay 320 is held continuously from grounded on closed contacts 203. That is, contact 573 is an X contact which means that it is held closed for a brief interval after contacts 574 close responsive to the release of error relay 570. Thus, for this brief interval until contacts 573 open, a pulse of grounded is extended over conductor RT to allot register relay 910 causing it to operate. Contact 575 is also an X contact which means that it too will be held closed brietly after contact 576 closes responsive to the release of error relay 570. During this brief interval of time, a pulse of grounded (l-) is extended over conductor MT to allot marking relay 970 causing it too to operate. This simulates the slow-to-operate functions of contacts 322 and 321, described above under the heading Register-Sender Seized.

Means must be provided for preventing the keying of further digits while the error relay 570 is operated since any such attempt would fail and hence an incorrect number might be transmitted. Therefore, contacts 578 of error relay 570 closes a circuit from grounded 500 through operated contacts 512 to light non-key lamp 348 and operate lamp relay 210 which in turn opens contacts 211 to prevent a false registration While the error key is operated. After the error relay 570 releases responsive to a release of the error key, contacts 578 open to release lamp relay 210 and extinguish non-key lamp 348.

In some cases, it might be possible that the error relay would be operated and released before all equipment has had time to release. In this case the register-sender would operate in an erratic and unpredictable manner. To forestall such an event, contacts 579 are provided to lock the error relay operated until all equipment is released. This feature provides an interlock whereby itis not possible to operate error relay 570 for such a brief interval of time that part of the equipment may be reheld. For example, let it be assumed that the error key is returned to normal and contacts 209 are open before dial start relay 850 has an Opportunity to release. In this case, contacts 852 will be closed and grounded is extended through operated contacts 579 to the error relay. This would hold relay 570 operated pending the complete release of relay 850 despite the fact that the error key had already been returned to normal. In like manner, marking relay 740 would hold error relay 570 operated until contact 748 opened. Ring control relay 650 would hold error relay 570 operated at contact 654 and main start relay 530 provides an interlocking feature at contacts 534.

First stop dial operation The register-sender is provided with means for extending one stop dial signal to prevent the sender from transmitting further digit pulses until distant equipment is prepared to receive these pulses. If a second stop dial signal is received from the distant end, it indicates that a switch has been directed into an overflow position, a busy line has been encountered, or perhaps for other reasons, the call may not be completed. Therefore, it is desirable to provide means for signaling one stop dial and further means for releasing all equipment in case a second stop dial is received. To test the proper operation of these stop dial features, the maintenance man is provided with a set of keys 330 and 331 which simulates stop dial conditions. The rst operation of one of these keys delays the sender until a later time when the stop dial signal is removed by returning the key to normal. The second operation of one of these keys releases all equipment. The two keys 330 and 331 are identical except that one is locking thus holding a stop dial or off-hook condition for a desired length of time, and the other is non-locking to provide for busy ashing. This is merely for the convenience of the maintenance man since he may prefer 

